The present invention relates to a thermally developable photothermographic light-sensitive material for making a printing plate (hereinafter, also referred to as a thermally developable photothermographic material or simply as photothermographic material), having high sensitivity and not employing wet processing, a printing plate made thereof and a preparation method thereof.
Up to this time, in the field of production of printing plate or of medical diagnosis, effluents accompanying the wet processing of image forming materials have become a problem in terms of operating properties, and recently, the reduction of processing effluents has been strongly desired also in terms of protection of environment and space saving.
Specifically, in the field of production of printing plate, the digitization of characters and images has been evidenced by much progress, and the interest in CTP (Computer To Plate), in which a printing plate is directly exposed without using prepress films, has increased greatly. However, the present CTP system, as a commercially available product on the market does not yet satisfy all of requirements with respect to processing speed, quality, working environment, etc. For example, a CTP system of a silver salt diffusion transfer type has a high exposure speed, but unfortunately has many problems in working environment, treatment of effluent and management of processing solutions due to the wet-type processing method which uses a developing solution. As a thermally developable type using a dampening solution, for example, even the two-sheet type CTP system (composed of a peelable sheet and a printing plate) described in such as JP-A 8-314143 and 8-314144 (JP-A refers to an unexamined and published Japanese Patent Application) has disadvantages of producing much waste material during use and short plate life of the printing plate surface.
On the other hand, a CTP system called a thermal type has a low sensitivity as the printing plate material requiring a high-powered laser for image formation, and consequently, it is difficult to increase the exposure speed. Further, some of this type requires pre-heating, which causes fluctuation in quality depending on the progress of heating until the development.
As a completely dry type system applicable to printing plates, there is a method in which the film surface is destroyed and peeled off utilizing a high-powered laser exposure; however, this equipment is expensive, the pieces of blown film may remain on the printing plate causing smudges in the non-image area, and further this system has the disadvantage of lower resolution.
As described above, presently, there is no complete dry type printing plate which is satisfactory with respect to the productivity as well as quality, therefore the requirements of the market have not been satisfied yet.
The invention has been achieved in consideration of the aforementioned problems. The object of the invention is to provide a thermally developable photothermographic material for making a printing plate, having high sensitivity without being subjected to wet processing, superior characteristics as a printing plate with respect to smudging in non-image areas, opening of shadow screen dots, recovery from smudge, as well as sufficient printing life; a printing plate made thereof and a preparation method of the printing plate.
The object of the invention has been achieved by the following constitution.
[Structure 1]
A photothermographic light-sensitive material for making a printing plate comprising a support having thereon a light-sensitive layer containing light-sensitive silver halide grains, organic silver salt grains, a reducing agent and a binder, wherein the organic silver salt grains comprise a organic silver salt having 10 or more of carbon atoms and the photothermographic light-sensitive material has an outermost layer at a light-sensitive layer side of the support having a coefficient of water absorption of not less than 0.7%.
[Structure 2]
The photothermographic light-sensitive material of Structure 1, wherein the outermost layer is the light-sensitive layer.
[Structure 3]
The photothermographic light-sensitive material of Structure 1, wherein the outermost layer is a light-insensitive layer.
[Structure 4]
The photothermographic light-sensitive material of Structure 3, wherein the thickness of the light-insensitive layer is within a range of 0.02 xcexcm to 1.2 xcexcm.
[Structure 5]
The photothermographic light-sensitive material of Structure 4, wherein the thickness of the light-insensitive layer is within a range of 0.05 xcexcm to 1.0 xcexcm.
[Structure 6]
The photothermographic light-sensitive material of Structure 1, wherein the coefficient of water absorption of the outermost layer is within a range of 1.5% to 50%.
[Structure 7]
The photothermographic light-sensitive material of Structure 1, wherein the light-sensitive layer has a contrast increasing agent.
[Structure 8]
A photothermographic light-sensitive material for making a printing plate comprising a support having thereon a light-sensitive layer containing light-sensitive silver halide grains, organic silver salt grains, a reducing agent and a binder and an outermost light-insensitive layer on the light-sensitive layer, wherein the organic silver salt grains comprise a organic silver salt having 10 or more of carbon atoms and the light-sensitive layer has a coefficient of water absorption of not less than 0.7% and the outermost light-insensitive layer has a coefficient of water absorption of not more than 0.7% and a thickness within a range of 0.005 xcexcm to 0.5 xcexcm.
[Structure 9]
The photothermographic light-sensitive material of Structure 8, wherein the light-sensitive layer has a contrast increasing agent.
[Structure 10]
The photothermographic light-sensitive material of Structure 8, wherein thickness of the light-insensitive layer is with in a range of 0.01 xcexcm to 0.2 xcexcm.
[Structure 11]
A printing plate prepared by a method comprising steps of:
exposing the photothermographic light-sensitive material of Structure 1,
subjecting the exposed photothermographic light-sensitive material to a thermal development.
[Structure 12]
The printing plate of Structure 11, wherein the printing plate has an exposed area and an unexposed area on the surface, and the exposed area and the unexposed area have different contact angles against water each other.